$ aptitude update したら、 W: GPG error: ftp.debian-unofficial.org etch Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 394D199524C52AC3 W: You may want to run apt-get update to correct these problems と出たので、 gpg --keyserver ftp.debian-unofficial.org --recv-keys 394D199524C52AC3 をしたら、 gpg: requesting key 24C52AC3 from http server ftp.debian-unofficial.org gpgkeys: no key data found for ftp.debian-unofficial.org/ gpg: no valid OpenPGP data found. gpg: Total number processed: 0 と出力されてしまいました。
